Tyzack 8-bit stereo sampler

sample 1
sample 2
sample 3

The pitchbend you hear is done with code similar to:

10 SAMPLE A,1
20 FOR I=1 TO 250
30 PITCHBEND I
40 NEXT
50 FOR I=250 TO 1 STEP -1
60 PITCHBEND I
70 NEXT
80 GOTO 20

A complete list of BASIC extensions can be found here.